“I think you’re going to be surprised at what developers can do when you unleash that community.”

Apple demonstrated using the watch to listen to music, with lyrics displayed on the watch face.

The company also demonstrated an app to open a garage door from afar to let in a family member who is locked out.

But one of the keys will be the health and fitness applications.

The watch has an accelerometer, a heart rate sensor and sensors for “a comprehensive picture of your all-day activity and workouts.”

It will prompt a user to get up and walk if sedentary too long.

A screen shot of the new Apple Watch after Apple chief executive Tim Cook unveiled it during a media event March 9, 2015 in San Francisco.

– All-day battery –

Cook boated that the device will have “all-day battery life” — or some 18 hours.

Entry price will be $349 in the United States, with costs up to $1,049 for extra features.

A solid gold limited edition will be priced from $10,000.

Initially, it will be available in Australia, Canada, China, France, Germany, Hong Kong, Japan, Britain and the United States.

Pre-orders will be taken from April 10.

Moor Insights and Strategy founder Patrick Moorhead, who attended the event, said “the secret weapon here is the ability to message each other by tapping on the watch, I think people, particularly kids, are going to go nuts over that.

“Apple has a big chance of success, and what that is going to do is set the bar for the experience that the entire smartwatch,” he added.

Jan Dawson at Jackdaw Research said Apple’s unveiling was “relatively unsurprising, with little new information other than price.”

Still, he said he expects Apple to sell around 20 million of the devices in 2015, and that this will “catalyze the overall smartwatch market and help other vendors even as Apple comes to enjoy levels of market share it hasn’t had since the iPod.”

More conservative, ABI Research expects Apple to ship 13.77 million units, just under 50 percent of the market.

At the event, Apple also unveiled a new Macbook laptop computer than weighs less than one kilo (two pounds), and a new initiative to use the iPhone to collect data for medical research, focusing on heart disease, diabetes, asthma, breast cancer and Parkinson’s disease.